This invention relates generally to an agitator for a fermentation and tissue culturing vessel and more particularly to an improved agitator for a fermentation and tissue culturing vessel wherein said fermentation and tissue culturing vessel is utilized as a microcarrier culture vessel.
The use of cell culturing techniques are widely known, and are vital to the study of animal cell structure and for the production of important medical material such as hormones, enzymes, antibodies, vaccines, etc. When using tissue and microcarrier cell culturing techniques, the cells are ultra-fragile in nature, and easily damaged during growth. The culturing of anchorage-dependent cells has proved particularly difficult and the use of microcarriers for this purpose has been developed. In microcarrier cultures, cells are grown as single layers on a surface of microcarriers, generally small spheres, which are in turn suspended in a culture medium by gentle agitation. A detailed description of microcarrier cell culture principles and methods and prior art systems of agitation may be found in the book "Microcarriers Cell Culture: Principles and Methods", Pharmacia Fine Chemicals, Sweden, December 1981.
As noted in the reference above, the highest yield for microcarrier cultures are obtained when the microcarriers are evenly suspended in the culture medium and are given the possibility for adequate exchange of gases with said culture medium. Erratic agitation or stirring motions must be avoided since these may lead to the detachment of the rounded mitotic cells from the microcarriers. For this reason, it is important to avoid exposing the culture medium and microcarriers to vibrations. On the other hand, agitation or stirring is essential to ensure that the entire surface of the microcarriers is available for cell growth, to create a homogeneous culture environment, to avoid aggregation of microcarriers and to facilitate the exchange of gases between the culture headspace and the medium.
A number of techniques have been utilized to provide suspension and aeration for the microcarriers and cells including spinner and rod-stirred vessels, the use of roller bottles, the use of rocking bottles, and the use of air-lift and fluid-lift culture medium systems. Efforts to improve agitation have included use of ball-tipped stirring rods fixed at one end and displaced in a circular path at the other end about a projection in the base of the vessel, and the use of paddle and plunger shaped impellers.
However, these systems have proven to be less than satisfactory, especially when employed in large scale commercial fermentation and tissue culturing assemblies, and are limited in the degree of control over the speed and force of microcarrier movement and aeration.
Accordingly, it is desirable to provide an agitator for use with a fermentation and tissue culturing vessel which is capable of keeping microcarrier cell cultures suspended to allow for exchange of gases, while minimizing the detachment of the growing cells from the microcarriers.